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Molecular Link between Sudden Infant Death Syndrome and Long-QT Syndrome Is “Proof of Concept”

When the parents of a 1-month-old infant found him blue and lifeless on an October day in 1995, they rushed him to the nearest hospital emergency room. Physicians there discovered the infant in ventricular fibrillation and, by countershock, were able to revive him. After doing so, they documented a marked prolongation of the QT interval.

That success and the parents’ quick thinking saved the child’s life and also provided Peter J. Schwartz, MD, with the perfect case in which to look for the molecular clue that he hoped would link long-QT syndrome with Sudden Infant Death Syndrome (SIDS) (N Engl J Med. 2000;343:262–267). Dr Schwartz, chairman of the Department of Cardiology at the University of Pavia and Policlinico San Matteo in Pavia, Italy, had already established a strong association between the 2 syndromes in a large prospective study of 34 442 newborns for whom he and his colleagues had recorded ECGs on the third or fourth day of life between 1976 and 1994 (N Engl J Med. 1998;338:1709–1714.).

In an analysis of 1-year follow-up data on 33 034 infants, the researchers discovered 34 deaths, of which 24 were attributed to SIDS. The infants who died of SIDS had longer corrected QT intervals than did the survivors and the 10 babies who died of other causes. The researchers found that 12 of the 24 babies who died of SIDS had prolonged QT intervals corrected for a heart rate >440 ms. Statistical analysis proved a strong association between the 2 conditions. In these cases of SIDS, the parents were apparently unaffected by long-QT syndrome.

In the 1998 article, Dr Schwartz pointed out that newborn ECG screening might permit the early identification of many infants at risk for SIDS and thus allow the use of drugs to prevent that sad occurrence. In his …